PORTLAND — If the question is, can a family with young kids take the Amtrak Cascades train from Seattle to Portland and manage a fun-filled, activity-packed weekend sans car, permit me to answer with another question:

Why would you drive?

With my husband, B.J., up for the challenge, and our kids, Bella, 9, and Jackson, 7, up for doing what they’re told, our foursome boarded the early morning train at King Street Station.

We soon discovered that if you’re weekend-vacationing without a car, Portland has got to be among the most accessible cities on the West Coast — and the Cascades train gives you the chance to look at a beautiful expanse of it along the way.

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Getting there

Amtrak may sometimes have a bum rap across the country, but the Cascades run has got it going on: fast and clean, with friendly, outgoing service from tickets-please to mind-your-step-as-you-deboard. We found ourselves crossing the Columbia River before we’d even tired of card games.

“I think it’s just fun relaxing,” said Gayle Lieberman, of Olympia, who boarded the train with her husband, Steve, and another traveling couple for a day trip to Portland. “This way none of us has to drive.”

“From Olympia you can’t beat this,” she added, indicating the view out the window where the Puget Sound coast flew by at about 50 mph. “It’s just a great trip.”

Portland is about 3 ½ hours by train from Seattle. Once you alight at Portland’s Union Station, you’ll find yourself at the northeastern end of downtown, in the old area called the River District, akin to Seattle’s Pioneer Square. An under-a-mile walk (or cab or bus ride) will bring you through Chinatown and the Old Town shops and into downtown proper.

Being there

The Portland Saturday Market: We started our weekend as many a Portlander might — at the Saturday Market. Near the Burnside Bridge, this street fair to end all street fairs happens with alarming frequency — every Saturday and Sunday for 10 months out of the year. It features hundreds of vendors, from the official (artists in the stalls) to the unofficial (buskers on every corner) to the indispensable (can you say giant pretzel?).

This spring the artisan market moved from its longtime site at the west end of the Burnside Bridge to a neighboring location in the newly renovated Waterfront Park and neighboring Ankeny Park; the Saturday Market is now centered at Southwest Ankeny Street and Naito Parkway. On Aug. 22, the market will celebrate the move (more information, www.portlandsaturdaymarket.com).

Oregon Museum of Science & Industry (OMSI): Our weekend in the Rose City coincided with the final days at OMSI for the traveling da Vinci Exhibition, and on-and-off rain made being outdoors a wet experience.

So needless to say, OMSI was packed, with a 30-minute line just to give them your admission money. Once patrons make it in the front door, though, the spacious museum handles crowds well, since there are so many places to put all the people.

We stuck with the basic admission ($9 kids, $11 for adults), which includes the physics, chemistry and life-sciences laboratories, cavernous hands-on jungles full of kid-pleasing delights like rocket-building stations, hair-raising static-electricity displays and a model bridge-construction site. Physics and engineering concepts descend on the kids without the youngsters even realizing they’re learning anything.

“They do a great job of bringing physics to a kid level,” said Michael Lee, a Portland resident who regularly visits OMSI with his 6-year-old son Rupert. He should know; Lee’s an actual physicist.

“We come here a lot.”

OMSI is on the east side of the Willamette, at 1945 S.E. Water Ave., accessible over the Hawthorne Bridge walking or via bicycle, and on the TriMet via the OMSI shuttle or several bus routes, including 10, 14 and 33 (more information, 503-797-4000 or www.omsi.edu).

Powell’s City of Books: Any trip to Portland must include a stop at the Rose City’s famous bookseller, the largest independent bookstore in the country. But you can’t have a million books without being somewhat overwhelming — to kids and adults.

My advice: Stick to the Rose Room (where you’ll find kids’ books) and just one other color (fiction is in the Gold Room), and make a final stop in the Coffee Room before you head out.

Powell’s flagship store is in the Pearl District at 1005 W. Burnside, accessible by foot, bus (several routes) or Portland Streetcar, which like other Portland transit, is free within Fareless Square (yep, Powell’s is in the Fareless Square; more information, 503-228-4651 or www.powells.com).

Waterfront Park: The park along the Willamette River draws foot, bike and stroller traffic better even than Seattle’s Green Lake, and it’s no wonder: With wide paths, a half-dozen places to cross the many-bridged Willamette, and lookout areas with downtown and Rose Garden vistas, it’s hard to imagine that this park was once just another place for cars. Nearly every weekend of the summer showcases a different festival here.

We found bicycles the best way to explore the park, with easy-peasy service and guidance from the crew at Waterfront Bicycles (10 S.W. Ash St., No. 100; 503-227-1719 or www.waterfrontbikes.net). An hour’s bike rental for our family came to $30 (and for our first-grader, that was plenty long enough), but you can make it longer and with different equipment (such as kid trailers or bike extensions for those with babies and preschoolers) depending on your needs.

One idea would be to combine your waterfront ride with your trip to OMSI, which is just over a mile away from Waterfront Bikes. The bike-rental crew will provide locks, helmets, bike maps and good advice (one priceless nugget: Cross the Willamette at the bike- and foot-friendy Morrison Bridge).